Method of making electromagnetic cores

ABSTRACT

A concentric magnetic core is assembled from a plurality of precut laminations formed into the desired shape and annealed. A pilot hole is then drilled in the centerline of the uncut yoke of the formed core. The core is then linked with a preformed coil or coils, with the pilot hole being used to insure positive registration of the laminations during lacing about the preformed coil or coils. A second pilot hole may be drilled within the cut yoke to aid in closing the joints if desired. A vibrating pilot pin may be used in the second pilot hole to assure positive closure of the joint in each lamination.

O United States Patent H 1 3,638,302 Wilk Feb. 1, 1972 [54] METHOD OF MAKING 2,595,820 5/1952 Somerville ..29/609 X ELECTROMAGNETIC CORES 2,927,366 3/1960 Link ..336/2l7 X [72] Inventor: Edmund J. Wilk, Adams, Mass. Primary Examiner john R Campbell [73] Assignee: General Electric Company Assistant Examiner-Carl E. Hall Attorney-Gilbert P. Tarleton, Francis X. Doyle, Melvin M. [22] Sept 1967 Goldenberg, Frank L. Neuhauser and Oscar B. Waddell [21] Appl. No.: 669,624

[57] ABSTRACT [52] U.S.Cl ..29/606, 29/609, 336/210, A concentric magnetic core is assembled from a plurality of 336/217 precut laminations formed into the desired shape and an- [51] lltLCl ..H0lf 7/06 d A il t h l is then drilled in the centerline of the [58] Field of Search ..29/605, 606, 609; 336/2l0, uncut yoke f the f d com The col-e is then hhkcd with a 336/2 l 217 preformed coil or coils, with the pilot hole being used to insure positive registration of the laminations during lacing about the [56] References preformed coil or coils. A second pilot hole may be drilled UNITED STATES PATENTS within the cut yoke to aid in closing the joints if desired. A

vibrating pilot pin may be used in the second pilot hole to as- Somerville sure positive cIogure of thejoint in each lamination. 2,467,867 4/1949 Somerville..... .29/606 X 2,543,089 2/1951 Zimsky ..29/605 3 Claims, 5 Drawing Figures BACKGROUND OF THE INVENTION This invention relates to electromagnetic cores and more particularly to concentric magnetic cores which are formed from a plurality of precut laminations.

In the electromagnetic core art, it is well known to form cores of precut laminations, such laminations being of progressive length and being assembled to form a closed electromagnetic core. Examples of these cores are shown particularly in U.S. Pat. No. 2,456,457; 2,456,458; 2,456,459 and 3, 1 86,067, all issued in the name of Somerville. A machine for cutting such precut laminations is shown in Somerville U.S. Pat. No. Somerville, In concentric cores, the laminations are usually cut in progressive lengths, formed into the desired shape and then annealed. The various laminations are then assembled around a formed coil or coils either separately or in packets. While concentric cores formed from precut laminations are very efficient, they do not provide the lowest loss characteristics possible due to lack of registration. As will be understood, in final assembly, each lamination of the core will not fall into the exact position or registration with the preceding lamination that it had when it was annealed. Cores in which the laminations are not in registration are under strain and thus introduce additional losses into the finished core.

It has recently been discovered that improved registration of finished cores can be obtained if pilot holes are drilled in the core after it has been annealed and before it is disassembled for lacing with a preformed coil. The pilot holes may be used during lacing of the core, that is, assembling it around a preformed coil to ensure almost perfect registration of each lamination with the preceding lamination.

. Therefore, it is an object of this invention to provide a more efficient electromagnetic core.

A further object of this invention is to provide an electromagnetic core in which the laminations in use have substantially the same registration as they had when annealed.

A still further object of this invention is to provide a novel method of making and assembling magnetic cores to provide improved registration between laminations.

Yet another object of this invention is to provide for pilot holes in electromagnetic cores to aid in accurately lacing such cores with preformed windings.

SUMMARY OF INVENTION According to the preferred form of this invention, a plurality of precut laminations are assembled into a concentric core which is then formed into the desired shape and annealed. While still in the annealed form, at least one pilot hole is drilled through the uncut yoke of the annealed core. The core is then disassembled and reassembled about a preformed coil or coils. During assembly, a pilot pin is inserted through the pilot hole to assure the proper registration of the various laminations.

The invention which is sought to be protected will be particularly pointed out and distinctly claimed in the claims appended hereto. However, this invention and the manner in which its various objects and advantages are obtained as well as other objects and advantages thereof, will be better understood from the following detailed description of a preferred embodiment thereof, especially when considered in the light of the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS FIG. I is a perspective view of a plurality of precut laminations of progressive length which may be used to form a concentric electromagnetic core according to this invention;

FIG. 2 is a perspective view of a formed concentric core ready for annealing;

FIG. 3 is a partial side view of the core of FIG. 2 showing the drilling of a pilot hole in the uncut yoke according to one form of this invention;

FIG. 4 is a partial side elevation view, partly in section, of a core and coil unit showing the preferred form of lacing a concentric core according to this invention; and

FIG. 5 is a partial sectional side elevation view of a core and coil structure made according to this invention.

DESCRIPTION OF PREFERRED EMBODIMENT In the preferred form of this invention, an electromagnetic core is formed from a plurality of precut laminations which are then formed into the desired shape and annealed. After annealing, the core is drilled in at least the uncut yoke to provide a pilot hole to aid in ensuring the registration of the various laminations during lacing with a preformed coil. The drilled core is disassembled and is then reassembled or laced about a preformed coil with a registration pin being inserted into the pilot hole to ensure the proper registration of the various laminations of the core. If desired, a second pilot hole may be provided in the cut yoke, the second pilot hole being used, preferably with a vibrating pilot pin, to ensure that each joint in the various concentric turns is completely closed. During lacing, various laminations may be locked together by spot welding a bridging lamination over the joint of the next lower lamination. After all of the laminations have been laced about the preformed coil or coils, a core results which is free of gaps and which is substantially perfect registration.

Referring now to the drawings in which like numerals are used to indicate like parts throughout the various views and referring first to FIG. 1, there is shown a plurality of precut laminations 10 which are of progressive length and which may be used to form the concentric core according to this invention. FIG. 2 shows the laminations I0 formed as a concentric core 12 which is shaped by means of wedges l4 and 16 into the desired form for the core. The concentric core may be banded such as by a band 18, formed, and then may be placed in an annealing oven to anneal the formed core to reduce or substantially eliminate all of the strain in the magnetic material which was caused by the folding of the material into the desired shape. The forming and annealing steps are, of course, well known in the art, for example, being described in the earlier discussed Somerville, U.S. Pat. No. 2,456,457.

After annealing into the desired shape, such as for example, the shape shown in FIG. 2 of the drawing, the annealed core is then drilled in the uncut yoke to provide a pilot hole through all of the laminations of the core. As is shown in FIG. 3, the core 12 may be clamped in a press indicated at 20 and the pilot hole drilled through each of the laminations by means of a drill 22. In some instances, it may be desirable to drill a second pilot hole in the cut yoke in the manner indicated in FIG. 4 of the drawing at pilot hole 24. The second pilot hole is found very useful to ensure positive closure of each of the joints in each lamination of the concentrically wound core 12. As is shown in FIG. 4, the second pilot hole 24, which is drilled in the cut yoke, is drilled so as not to intersect any of the cut edges of the precut laminations. Of course, as will be understood, this may readily be accomplished by stepping each of the laminations 10 in a manner such that the joints indicated at 26 in FIG. 4 will fall sufficiently far from the centerline of the cut yoke indicated at 28 so that hole 24 will not encounter any of the cut edges 26.

The first drilled pilot hole is indicated in FIG. 4 as hole 30, which, as can be seen, is drilled in the uncut yoke of core I2. As will be understood, it is preferable that the hole be located on the centerline of the laminations in order to minimize any possible circulating current losses. However, it should be understood that, if desired, the pilot hole, such as hole 30, may be located in either the yoke or the leg. Where a particularly heavy build core is being laced with a preformed coil or coils, it may be desired to secure partial assemblies. This may be done by use of a bridging spot weld in the manner shown at FIG. 4. As will be understood, after a plurality of concentric laminations 10 have been assembled about a prefonned coil, such as indicated at 32 and 34 in FIG. 4, a pilot pin 36 may be inserted in registration hole 30and pushed against the insulation members 38 of the coils 32, 34. The registration pin 36 is designed so as to snugly fit into the hole 30 and properly align the holes of each lamination 10, such that the laminations will be in perfect registration with each other. Once pin 36 is inserted in hole 30, it is not removed until all laminations in core 12 are assembled and in proper registration. For this reason pin 36 is also designed with a tapered end 40 to facilitate threading laminations 10 over pin 36. After assembly of a number of single laminations or packets, an overlapping lamination, that is, a lamination which overlaps a preceding joint may be welded to each side of the joint as is indicated at 42 in FIG. 4, to secure the partial assembly prior to assembling more of the concentric laminations.

As will be understood, when desired, the second pilot hole 24 may be utilized with a registration pin 44 to ensure proper closure of each of the joints 26. The registration pin 44 is similar to pin 36 and has a tapered nose as is indicated at 46. When the pin is inserted in pilot holes 24, the pin ensures proper closure of the joints 26 in each of the assembled laminations. if desired, the registration pin 44 may be vibrated by any type of vibrating means to ensure the proper insertion of pin 44 and proper closure of joints 26. Of course, it will be understood, that, if desired, the concentric core may be-provided with inner and outer overlapping turns and these turns may be utilized by spot welding to lock the assembled core in position. If the overlapping turns are not used, then the core may be either banded in the manner indicated at 18 in FIG. 2, or insulated or nonmetallic locking pins may be inserted in the pilot holes to secure each of the laminations in the desired position.

FIG. 5 shows a core and coil assembly according to this invention. As is shown in FIG. 5, the concentric core 12 is laced about the preformed coils 32 and 34 and a pilot hole 30 is provided in conjunction with a pilot pin 36 to ensure proper registration of each of the laminations as they are assembledabout the preformed coils 32 and 34. Of course, it will be understood, that a pair of cores could be laced about a single preformed coil or that any other single or three phase construction could be used, as desired. The use of the pilot hole 30 and the pilot pin 36 to ensure the adequate registration of each of the laminations in the core will be the same regardless of the construction. When desired, a second pilot hole as is indicated at 24 in FIG. 4 may be used to secure proper closure of each of the joints in the individual laminations in the manner previously discussed.

From the above description, it will be apparent that this invention provides a core which may be assembled with a preformed coil or coils while obtaining substantially exact registration of all the laminations in the core. Further, according to this invention, the core may be provided with positive closure of the joints by use of a second pilot pin. While the invention has been illustrated and described with reference to the present preferred embodiment, it will be clear to those skilled in the art that it is not limited thereto. The scope of the invention will be apparent from the appended claims.

What is claimed as new and which it is desired to secure by Letters Patent of the United States is:

l. A method of assembling a concentric, annealed electromagnetic core with a preformed coil which comprises;

a. forming a plurality of precut laminations into a desired form of a concentric core,

b. annealing said core,

c. drilling a first pilot hole in an uncut side of said core,

d. drilling a second pilot hole in the cut yoke of said core,

e. disassembling said core and lacing a number of laminations about a preformed coil,

f. placing a pilot pin in said first pilot hole of said laced laminations to insure proper registration of said laminations,

g. placing another pilot pin in said second pilot hole to insure proper closure of the joints of said laminations, h. continuing to lace said laminations over said pilot pins and about said preformed coil until said core is entirely laced about said coil.

2. A method of assembling a concentric, annealed electromagnetic core with a preformed coil as set forth in claim 1 in which an insulated pin is placed in said second pilot hole after said core has been laced with said preformed coil to secure said laced laminations.

3. A method of assembling a concentric, annealed electromagnetic core with a preformed coil as set forth in claim 1 in which an insulated pin is placed in each of said one pilot hole and said second pilot hole after said core has been laced with said preformed coil.

UNITED STATES PATEN OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 3 ,3 Dated February I, 1972- Inventor' (s) Edmund J. Wilk- It is certified that error. appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

col. 1, line 15 "Somerville" should be 2,369,617

Signed end sealed this 6th day of June 1972.

(SEAL) Attest:

- EDWARD M.FLET0HER, JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents UNITED STATES PATENT OFFICE I CERTIFICATE OF CORRECTION Patent No. 3: 3 ,3 Dated February 1, 1972 Invent or(s) Edmund J. Wilk It: is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 1, line 15 "Somerville" should be 2,369,617

Signed and sealed this 6th day of June 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Commissioner of Patents Attesting Officer 

1. A method of assembling a concentric, annealed electromagnetic core with a preformed coil which comprises; a. forming a plurality of precut laminations into a desired form of a concentric core, b. annealing said core, c. drilling a first pilot hole in an uncut side of said core, d. drilling a second pilot hole in the cut yoke of said core, e. disassembling said core and lacing a number of laminations about a preformed coil, f. placing a pilot pin in said first pilot hole of said laced laminations to insure proper registration of said laminations, g. placing another pilot pin in said second pilot hole to insure proper closure of the joints of said laminations, h. continuing to lace said laminations over said pilot pins and about said preformed coil until said core is entirely laced about said coil.
 2. A method of assembling a concentric, annealed electromagnetic core with a preformed coil as set forth in claim 1 in which an insulated pin is placed in said second pilot hole after said core has been laced with said preformed coil to secure said laced laminations.
 3. A method of assembling a concentric, annealed electromagnetic core with a preformed coil as set forth in claim 1 in which an insulated pin is placed in each of said one pilot hole and said second pilot hole after said core has been laced with said preformed coil. 